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20,000 caterpillars are let loose on the prairie, boosting numbers of threatened butterfly

Regal fritillary caterpillars munch on violets
Michele Skalicky
Regal fritillary caterpillars munch on violets

Effort to increase the population of a threatened butterfly in southwest Missouri is underway.

A long table in Temple Hall on the Missouri State University campus is filled with rows upon rows of violets growing in pots. On another table, hungry caterpillars in various stages of development munch on plants in zippered mesh bags.

Most of the caterpillars are the larvae of the regal fritillary, a type of butterfly found only on original, unplowed prairies that contain violets. Retired MSU biology professor Chris Barnhart is raising the caterpillars with the help of students and in collaboration with the Missouri Department of Conservation.

Barnhart said they embarked on a project to raise regal fritillary caterpillars after they were proposed for federal endangered status.

They’ve been lost to most of their range as prairies have disappeared.

"If one percent of prairies are left, well, probably one percent of regal fritillaries are left, too," said Barnhart.

Chris Barnhart holds a regal fritillary butterfly
Michele Skalicky
Chris Barnhart holds a regal fritillary butterfly

Their habitat is not continuous anymore; they rely on unplowed prairies for survival. There are prairie remnants that are protected, and regal fritillary butterflies can be found on some of them. The caterpillars feed on violets, and the adults feed on nectar from various prairie plants.

Steve Buback, natural history biologist with MDC, says regal fritillaries will occasionally fly fairly long distances to find food—but it’s become more difficult for them to survive.

"You know, the odds of them stumbling upon another prairie as they fly around is pretty low," he said. "And so we had the idea that we could kind of augment populations and restore them to areas where they had been locally extirpated."

Buback turned to Barnhart, who has had success raising great spangled fritillaries.

After a planning and preparation phase, regal fritillary butterflies were collected last September at Compton Prairie in Missouri.

The team collected 10 female regal fritillary butterflies and took them to MSU, where they were fed every day until they lived out their lives.

Female regal fritillaries lay 2,000 eggs, one egg at a time, just once a year in September.

Chris Barnhart points to a tiny regal fritillary caterpillar
Michele Skalicky
Chris Barnhart points to a tiny regal fritillary caterpillar

The butterflies Barnhart and his team collected laid their eggs on pieces of shredded paper mixed in with violets. A total of 20,000 eggs, which Barnhart said was far more than expected, was collected and sorted into condiment cups. After they hatched, they were placed in a refrigerator to mimic winter.

And this spring, when they were brought out of the cold, they were placed on violets where they began to eat…and eat. They grow from about the size of a grain of rice when they hatch to about two inches long. Wickman Gardens donated lots of violets for the caterpillars to eat.

On Tuesday, they’ll be taken to prairies in Polk County where they’ll be released onto violets—one per plant, said Barnhart.

"And when they're finished with that one hopefully they'll go and find some more. But we don't expect all of them to survive because there are ants, and there are spiders, and there's praying mantis, and there's birds—there's all kinds of things that are going to reduce their numbers," Barnhart said.

Buback said they don’t yet know if releasing regal fritillary caterpillars is going to be the most successful method, "so, we'll just have to try it and see and hope for the best."

They plan to release adult butterflies, too.

And they’ll monitor the prairies to see if the releases are successful. They chose prairies with a healthy population of violets, but ones where there are no longer any regal fritillaries. That way, if they see any regals, they’ll most likely be ones that were released by the biologists.

A regal fritillary butterfly gets nectar from a flower
USFWS Mountain Prairie
/
Flickr
A regal fritillary butterfly gets nectar from a flower

Buback said it’s important to make sure no species is allowed to go extinct. Regal fritillaries, he said, are an iconic part of Missouri’s natural heritage.

"These butterflies are large, conspicuous, you know, they're similar in size to a monarch," he said. "When you're out on the prairies, if you know what you're looking for, you really can't miss them. And, you know, they're a sign of a functioning ecosystem, so a prairie that supports regal fritillaries is what we would consider a healthy prairie."

Chris Barnhart holds a regal fritillary caterpillar
Michele Skalicky
Chris Barnhart holds a regal fritillary caterpillar

Barnhart has always had a fascination with butterflies, which led him to become an entomologist.

And he’s fascinated with both regal and great spangled fritillaries, in part because, while the males die within a month of emerging, the females have to last all summer long. It’s rare for a butterfly to live more than two weeks. To survive from May to September regal and great spangled fritillaries take care of themselves. He said they’re cautious, they rest during the day, they feed at particular times, and they have a roost to go to.

"They live a life that you would expect they'd have to live to survive that long," said Barnhart.

He feels optimistic the project to release more regal fritillaries on the landscape will be successful and will make a difference to the regal fritillary population.

Buback said, if funding is available and this project is successful, they’ll likely do it again this fall.